This application, in response to PAR 10-038, will evaluate of an implementation model that engages high school students in Wellness Council planning to achieve obesity-related health recommendations. The implementation planning will apply a participatory action research approach to empower students as stakeholders and to facilitate collaborative planning by school Wellness Councils, facilitated and supported by the HealthCorps coordinators. To facilitate achievement of the 2010 Dietary Guidelines, we will implement a process to enable schools to select toolkit strategies and elements from evidence-based curricula (e.g., Physical Activity for Teenage Health (PATH), which includes implementation strategies using low-cost resources). The 2010 Dietary Guidelines obesity-related behavioral recommendations for youth include: decreasing sugary beverage intake; increasing frequency of breakfast; increasing vegetable and fruit intake to 2 1/2 cups per day with fill half your plate with fruit and veggies educational message; decreasing frequency of fast food meals; becoming physically active (goal of 1 hour per day); and reducing sedentary behavior time (<2 hour day). The social ecological framework provides the foundation for a two-tiered integrative approach which addresses barriers faced by the school (micro-environmental level) and by the students (individual level). At the school level, implementation barriers will be identified by (or brought to) the school Wellness Councils (e.g., crowded gym, lack of equipment, food service issues) using a toolkit approach patterned after the Alliance for a Healthier Generation school toolkits. At the student level, the toolkit will focus on barriers to implementation of lifestyle changes. Options for the student toolkit include tailored student support via social media e.g., Facebook, text message or email to address common internal barriers, such as self-efficacy and motivation, and external barriers in the home, school and community environment. Using a stepped wedge cluster randomized trial design to roll out testing of the participatory implementation model, we will randomly select from among the NYC HealthCorps high schools each year. This design will allow us to assess the impact of wellness programming on students, in relation to their school environment. To evaluate how our participatory implementation model addresses wellness barriers in diverse, complex school settings, we will employ system dynamics modeling (SDM). This method will synthesize both quantitative and qualitative assessment results into simulation output that will show the process by which wellness programming is adapted and sustained over the intervention period. We hypothesize that students in the participatory implementation schools will achieve better dietary and physical activity health habits than students in waitlisted HealthCorps control schools. Secondary hypothesis, students will achieve key health behaviors after their NYC HealthCorps school is randomized to participatory implementation compared to students in the waitlisted HealthCorps control schools; Tertiary hypothesis: Using system dynamics modeling to evaluate implementation will facilitate more robust dissemination. The simulation analysis will apply the RE-AIM framework: (Reach (participation rates), effectiveness (outcomes), adoption (acceptability), implementation (intervention fidelity), and maintenance (sustainability of lifestye changes by students and programs by schools).